Initial updates to migrate processor metrics to obsreport package, ie.: the new metrics.
Cleaned-up a bit some of the processor metrics and spelled out the rule names for new metrics.
Related to https://github.com/open-telemetry/opentelemetry-collector/issues/141
Testing: Added test for the processor common metrics, validated manually that legacy metrics were still working
* Move probablistic and tail sampling processors under common parent
Phase 1 change to defining sampling processors. This structure follows
what is done in the receiver and exporter folders.
* Import from proper directory for sampling
Bogdan Drutu
Jay Camp
Bruno Garcia
Paulo Janotti
Paulo Janotti
Steve Flanders